This invention relates to an ink jet head, and in particular, to an ink jet head having a head chip in which drive walls made up of an piezoelectric element and channel portions are arranged alternately, the inlet and outlet of the channel portions are arranged in an opposite manner on the front side and rear side respectively, and by the application of a voltage to said drive walls to deform said walls by a shearing force, ink drops in the channel portions are jetted.
Up to this time, it is known to the public, as an ink jet head of a shear-mode type jetting ink drops in the channel portions by the application of a voltage to the drive walls partitioning the channel portions to deform the drive walls by a shearing force, an ink jet head which can be obtained as one of a number of heads produced from a wafer with its productivity extremely improved, owing to its actuator being made up of a head chip of what is called a harmonica type in which drive walls made up of a piezoelectric element and channel portions are arranged alternately, while the inlet and the outlet of the channel portions are arranged in an opposite manner on the front side and the rear side respectively (patent literatures 1 to 3).
The channel portion of such an ink jet head is of a straight type having its size and shape approximately not changed in the length direction from its inlet to its outlet, and at its rear side, an ink manifold as an ink supply room forming member making up an ink supply room for supplying ink to the channel portion is fixed; therefore, it is difficult to electrically connect a lead wire for applying a voltage to a drive electrode formed on each drive wall to a drive circuit.
For example, in a technology described in the above-mentioned patent literatures 1 to 3, through holes are formed in one of the upper and lower base plate oppositely attached to the drive walls as holding them from the upper and lower direction, and by the utilization of these through holes, lead wires connected to the respective drive electrodes are made to come out to the outer surface of the head chip; however, because the operation to form such through holes for the respective channel portions is troublesome, and on top of it, an operation for connecting lead wires from the drive circuit to the lead wires formed in these through holes is required, a structure to make it possible to carry out more simply an electrical connection with the lead wires from a drive circuit is desired.
Especially, in recent years, for the purpose of recording a higher-quality, higher-definition image, it has been progressing to make the nozzle density higher, and also it has been considered an ink jet head having a head chip structure whose nozzle density is made higher by the formation of a plurality of nozzle rows in the nozzle plate through the formation of the drive walls and the channel portions in a multi-stage manner in the vertical direction; in particular, in the case of a head chip having a structure of three or more stages stacked in the vertical direction, there has been a problem that it becomes more difficult to electrically connect lead wires for applying a voltage to the respective drive electrodes located at the middle position to a drive circuit.
Further, on the rear surface of the head chip, an ink manifold making up an ink supply room for supplying ink to each channel portion from its inlet side (the reverse side to the nozzle plate) is fixed with an adhesive; however, in the above-mentioned conventional technology, it is necessary to bond fixedly the rear surface and the ink manifold by means of a coating of an adhesive in a way such that the bonding area does not overlap each channel portion by the utilization of the space surrounding the channel portions. However, the thickness of a head chip is only several millimeters or so, and in the rear surface of such a head chip, the area for bonding capable of being coated with an adhesive to a degree not to produce a part of the adhesive being pressed out has a space of only about 0.5 mm at the largest. Hence, when an ink manifold is bonded fixedly with the rear surface of a head chip by means of an adhesive, it is necessary to carry it out with the adhesive carefully coated on a minute space in such a manner as not to be forced out, but this raises a problem in terms of productivity. In this case, also it can be considered to secure a broad coating space of an adhesive by the upper and lower base plates being formed to be larger (thicker), but it results in a head being made larger-sized uselessly. For this reason, it is desired an ink jet head having a structure to make it possible to achieve a further improved productivity without making its head chip large-sized uselessly.
[Patent literature 1] The publication of the unexamined patent application 2002-103612
[Patent literature 2] The publication of the unexamined patent application 2002-103614
[Patent literature 3] The publication of the unexamined patent application 2002-210955
Therefore, it is an object of this invention to provide an ink jet head of high productivity which makes it possible to carry out the electrical connection of the drive electrodes in the respective channel portions with lead wires from a drive circuit in a simple manner, and also makes it possible to carry out the formation of an ink supply room for supplying ink to the inside of each channel portion easily.